Extendible shelters have taken various forms. In the main, however, when kits are used, they are connected by conventional permanent fastening means, including nails, nuts and screws and the like. The use of permanent fasteners often make it inconvenient to knock down the shelter for removal to a different site and often result in the loss of some of the parts used to refasten or connect the various parts at a new site.
Other shelters used heretofore have generally not included means for sealing against the weather and other environmental conditions at the joints where the various panels are joined.
Another disadvantage develops in many prior shelters when they have to be built on unlevel ground, which is the normal situation. Unlevel ground poses a number of problems when a number of units have to be added to each other to produce a relatively large shelter.
Most "add on" shelters assembled in the field require special tools, which sometimes are not readily available. Also, indexing and supporting a unit to be added to a prior assembled unit pose special time consuming problems.
Another problem involved in many prior art extendible shelters is that the parts involved are so heavy or cumbersome that they cannot be readily handled by two men, for example.